<?php

$a = "12.20";
$b = "10";
$array1  = array($a,$b);
$array2 = array("12.2","10.00");
$var1 = array_map('floatval',$array1);
$var2 = array_map('floatval',$array2);
$diff1 = array_diff($var1,$var2);
var_dump($diff1);